The aim of these research efforts is to explore the psychobiology of cognition in man. We attempt to define the psychobiological determinants of the various components of cognition. Studies have been designed to understand the specific and discrete mechanisms which account for the acquisition, processing, encoding, consolidation, and retrieval of experience. Other studies have also begun to examine the meta-cognitive processes (self-monitoring operations) involved in learning and memory. Experiments are also designed to further our understanding of the biological and psychological determinants of impaired cognition in psychiatric and neuropsychiatric patients. Specific forms of central nervous system dysfunctions (e.g., as defined by type of lesion in neuropsychiatric disorders) may affect distinct components of cognitive processing. Similarly, psychoactive drugs that affect discrete aggregates of neurons, may alter different aspects of cognition and information processing and serve to model forms of cognitive dysfunctions in man. Based on empirical studies of clinical populations (e.g., depression, Alzheimer's disease, Huntington's disease, Korsakoff's disease, forms of learning impairments in children) and several types of psychoactive agents (cholinergic drugs, noradrenergic drugs, serotonergic drugs, drugs that alter GABA activity, neuropeptides), it has been possible to begin to define the psychobiological relationships between semantic and episodic memory, encoding processes, and effortful (active) cognitive operations as opposed to automatic cognitive processes.